Coherent structures in the wake of sphere at subcritical Reynolds numbers via wall-modeled stress blended eddy simulation

The numerical simulation of flow past a sphere at subcritical Reynolds numbers presents significant challenges, particularly in accurately resolving and representing complex coherent structures. These include the Kelvin–Helmholtz instability in the shear layer and large-scale vortex shedding in the wake. Additionally, further investigation is needed to understand the mechanisms behind the low-frequency characteristics observed in the flow. This study introduces a wall modeled stress-blended eddy simulation (WM-SBES) approach to conduct high-fidelity computational fluid dynamics simulations of these intricate blunt-body flows. Unlike conventional detached eddy simulation (DES) methods, which rely on the assumption of equilibrium flow, WM-SBES directly combines Reynolds stress within the framework of Reynolds-averaged Navier–Stokes (RANS) and large eddy simulation (LES) subgrid stress at the stress level. This allows for the selection of appropriate RANS modes and LES models, respectively, according to specific fluid conditions. Simulations conducted at a subcritical Reynolds number of Re = 10 000 demonstrate that the proposed method effectively captures the complex coherent structures within the flow field. Furthermore, an analysis of the spectrum characteristics of fluctuations of the recirculation zone in the wake confirms that the observed low-frequency behavior results from the periodic shrinkage and enlargement of the recirculation zone.